[Libre-soc-isa] [Bug 960] OPF ISA External RFC ls003 - maddedu and divmod2du

[bugzilla-daemon at libre-soc.org]

https://bugs.libre-soc.org/show_bug.cgi?id=960

--- Comment #17 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #16)
> for muledsbs (signed bigint * signed word), we may be stuck with the
> non-independently-parallelizability (sorta, OoO can run multiple vectors in
> parallel if the queues are big enough) because it's looking like 64 bits
> isn't enough carry bits, we may need it to also read/write CA:
> working pseudocode so far:
> 
> def muledsbs(ra, rb, rc, ca):

note that my current plan for how muledsbs is used is:
# mul little-endian signed bigint in r4-5 by signed word in r3, result in r4-6
setvl VL=2
addic 0, 0, 0 # clear ca
li 6, 0 # clear r6
sv.muledsbs *4, *4, 3, 6
# product now in r4-6

if you can come up with a way to implement muledsbs without needing ca and
without instead needing to compute rc // rb, that'd be awesome!

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